The present invention relates to a telecommunication network and a state propagation method for monitoring and performing the state propagation of various objects of network elements.
Operation, maintenance, and administration functions exist in any telecommunication network. The GSM (global system for mobile communication) specification covers these functions. The general philosophy of telecommunication management networks is that all management operation will take place on an abstract representation of network elements. The information model of GSM, see M. Mouly, M. B. Pautet, xe2x80x9cThe GSM System for Mobile Communications,xe2x80x9d 1992, gives an abstract system view.
Network elements are modeled as managed objects (MOs). More generally, managed objects represent anything which is managed. For example, the information model also covers managed objects such as tests or observations. The objects themselves are instances of classes. A class is a description of the attributes, properties, and actions which are common to all objects belonging to the class. The concept of generic GSM object classes is very close to object oriented programming.
Generic states and status attributes are used to describe the operability and availability of the managed objects. For instance, the state of a managed object may be locked, disabled or degraded. Between the managed objects there may exist complex relationships. The relationship stem from the GSM containment tree, the hardware architecture, the wiring of the boards, the grouping of boards to functional units etc. Generally, any state transition of a managed object may result in a sequence of state changes of other related managed objects.
These dependencies are described as relationships in the source code of a maintenance software for a network element. This code is complex and difficult to adapt in case of a hardware modification of the network element. Large numbers of managed objects cause a breakdown of this concept, especially if all multiple faults are considered.
It is an object of the present invention to identify a telecommunication network and a state propagation method which manage even a large number of managed objects and which guarantees the state consistency of all managed objects even in the case of multiple faults.
According to the invention, a telecommunication network comprises an operation and maintenance device and a plurality of network elements, each of the network elements having hardware objects. At least one network element communicates state changes to the operation and maintenance device. The operation and maintenance device comprising: a memory device for separately storing a state dependency graph with objects, states of the objects and operators, and for also storing a set of rules allocated to the operators; and a processing device, which processes the communicated state changes by applying the rules to the operators of the graph and calculates new states of all objects that depend on the communicated state changes.
The correct calculation of all managed object states is the basis of a reasonable operation, maintenance and administration of the telecommunication network and its elements. The present invention shows a new and versatile state propagation method for the network elements such as base stations of mobile communication systems. The algorithm may also be applied to the whole telecommunication system or parts of it with at least two network elements.
The proposed state propagation algorithm automatically calculates all state transitions that follow from the state change of a target managed object. This state change has been communicated to the operation and maintenance device. This device may be part of a network element to be managed or may be regarded as a supplementary network element in form of a operation and maintenance center.
The memory device of the operation and maintenance device stores the relationships between the managed objects modeled by a general dependency graph. The dependency graph consists of managed objects and operators, like AND/OR functions describing the type of relationship between managed objects.
The graph may be created automatically using a simple description language as input. The concept of a general or a maximal graph allows the simultaneous treatment of different hardware configurations. The propagation algorithm is basically a guided graph traversal both in a forward direction (from initial to terminal nodes) and a backward direction. During the traversal the new states of the managed objects are calculated. The next state calculation is based on implication rules. It is not necessary to recalculate all states if parts of the graph are not influenced by a state change.
The rules, which are associated with the operators, are either stored in truth tables or in general decision diagrams. The method can easily be tailored to new relationships and requirements. The latter requires simply the adaption of the dependency graph and the rules.
The signaling between different network elements and the operation and maintenance device is reduced significantly using the state propagation algorithm. A state change of one of the managed objects normally causes state changes of other managed objects. These new states of the dependent objects do not have to be communicated too the operation and maintenance device. The communication of just one state change may be sufficient.
Another advantage of the present invention is the concentration of the state dependencies in one graph. By applying forward and backward rules the need for a greater split in different graphs is reduced. In addition, less memory space is required.